edfair,
<<...Would it be more correct to say that anybody could have figured out the hidden APIs had they taken the time and effort to trace them? >>
I can't see how or why. First, the p5 and higher processors have more and bigger registers than the pre-PC days, and reverse-engineering these large .dlls would be a waste of time, since, as was stated by CajunCenturion, MS could change them at will and then all the (probably thousands) of man-hours would be wasted and they'd need to start from scratch, send out patches to millions of customers, all the while MS engineers would be snickering and snorting with snot dribbling from their noses.
There is no question that this is what they've done and for the stated obvious reasons. Look at simple human psychology. Some men have been faced with a moral question and have killed for a few bucks. Other men have faced those questions, judged the reward against the crime and killed for millions--the risk/reward spread being much larger.
Now, take Bill Gates. His 'crime'--and note in these posts that it's not even known if it's actually a crime--was to create a crippled api set for his competition to use. The reward was billions and billions of dollars and world domination in the one of the most lucrative businesses ever. Basically little or no risk and the largest reward ever imagined.
Does anyone think he thought about that and said 'No, that would be unfair'? Please.
--Jim